The main purpose of white LED in the future is thought to be the substitution for the traditional lighting, especially lighting equipment such as tungsten bulbs or fluorescent lights. This is because LED has more advantages than the traditional lighting; such as its small size, low heat emission, low energy consumption, longer longevity, shorter response time, and zero mercury pollution. Therefore, in addition to being employed in traditional lighting in the future, LED also has wide applications in various industries, such as being used as the indicator and internal lighting of cars, dashboard, as well as LCD backlight panel.
There are currently two major techniques for producing white LED globally; the first one is mainly employed in commerce right now, which produces white light by using a blue light emitting diode to excite yellow phosphor powder. However, the phosphor powder required by this technique is owned by companies in Japan and the U.S. For example, a yellow phosphor powder that is abbreviated as YAG, and with the composition of (Y, Ce)3Al5O12, was developed by Nichia Corporation of Japan. On the other hand, a second technique that is still being developed now produces white light by using the UV-LED of the wavelength less than 400 nm to excite phosphor powders with three different RGB colors. Because more than one phosphor powders are required by this technique, it is not only necessary to find the phosphor powders that can complement one another, whether the deterioration rates of various phosphor powders are uniform must also be considered, which is an important factor that affects the quality of the resultant white light. Therefore, it can be concluded from above that phosphor powder will play a crucial role in the development of white LED, no matter in the current white LED techniques or the ones in the coming future.
The luminescence properties of a phosphor powder is related to its chemical composition, a phosphor powder of the same chemical composition and structure but with different luminescence properties has not yet be developed so far.